The draw means a replay at Stamford Bridge must be worked into an already-congested fixture list, which is seemingly dependent on Chelsea's progress in the Europa League - with the club to face Steaua Bucharest on Thursday.

If Rafael Benitez's side lose, the replay is set to be played during the first week of April, even though UEFA prefers major countries not to arrange domestic fixtures at the same time as their competitions.

If Chelsea are able to overturn a 1-0 first-leg deficit, then a fixture pile-up would cause a real headache, in particular with the forthcoming international break.

United boss Sir Alex Ferguson said after Sunday's 2-2 draw at Old Trafford: "I don't know when the replay will be played, probably May!"